There is some disagreement amongst builders and plasterers as to how (or whether, even) to clean a plasterer’s hawk…
Wonkee Donkee advises that you clean your hawk promptly with water and a rag after each use.
If the plaster or mortar has dried onto the tool, you can soak it in water to soften the mixture.
Store the hawk with the plate upright on a shelf or tool rack to allow the surface to dry out completely. Handles can be removed, where detachable, to save on space.
Please note: Some users don’t bother cleaning their plastic hawk as they say the residual plaster gives it a better grip. Just give them a quick wipe after use, they advise, and gently chip off the old plaster or buy a new one when build-up makes them too heavy!